For purposes of mass-rearing fruit flies, nutrient intake through artificial diets is a challenge, artificial food content and processing should promote sufficient absorption and availability to ensure fly fitness. Bulking agents play an essential role in creating a quality diet, but its physical characteristics, such as particle size, may establish a better microenvironment for feeding and development. Currently, there is a lack of information about protein metabolism in mass-reared fruit flies. Therefore, we evaluated whether the particle size of the bulking agent affects the absorption and excretion of the proteins, as well as their effect on the life-history traits of Anastrepha obliqua. We determined the protein content of hemolymph and feces, as well as the presence of nitrogen end-products as indicators of their level of absorption in a diet elaborated with coarse and fine corn cob particles as a bulking agent. The bromatological composition showed that coarse particles increased the bioavailability and content of crude, digestible, and soluble protein for the diet and hemolymph protein of larvae alike. We found an inverse relationship between the protein content of the hemolymph and feces of the larvae. Ammonium was determined to be a product of the catabolism of proteins. Also, A. obliqua improved its development (yield and pupal weight) and fitness (adult emergence and flight ability) when larvae were reared on a coarse particle diet. In conclusion, a diet elaborated with a coarse bulking agent features increased protein bioavailability and nutritional quality, which, in turn, increases the life-history traits of A. obliqua.
Although the bulking agent is categorized as ‘inert’, it could modify protein bioavailability and nutritional quality. In this study, the main goal was to determine if the bulking agent modified the protein:carbohydrate (P:C) ratio and bioconversion from diet biomass to larval biomass of Anastrepha ludens. The diet was altered only by modifying the type of bulking agent (corncob powder, coconut fiber, carrot fiber, oatmeal) added without changing the composition and concentration of the other components in the formulation. This allowed reclassification of the food matrices according to P:C ratios of 1:30, 1:35, 1:64, and 1:93. A food matrix with a high P:C ratio promoted a high protein and carbohydrate content in the larval hemolymph and immediately influenced the life-history traits of the larva or delayed them in the adult. The present study indicated a positive relationship between the P:G+T (glucose+trehalose) ratio in the larval hemolymph and the P:C ratio in the larval diet. Our results highlight the importance of including the optimum and real P:C ratio in whole fresh larval diets, since considering only the theoretical concentration of the formulation is not enough to understand the variation in key life-history traits. In addition, the bioconversion index should be included as an indicator of the efficacy of larval diets for mass rearing insects. A diet with high cost-effectiveness should be evaluated by taking into account flying flies as the end product of the mass rearing process to enhance operational SIT programs.
Few studies have focused on how nutrition affects the bioavailability and investment of protein during the metamorphosis of tephritids. Our study allowed us to observe how the type and particle size of the bulking agent affected the protein composition in the hemolymph of the larva and adult of Anastrepha obliqua. Results indicated that, true protein bioavailability and protein profile was greatly modified by the bulking agent and its particle size. The physical structure of the food matrix affected the content of crude fiber (F), crude protein (P), F/P ratio, non-protein nitrogen, ammoniacal nitrogen, and α-amylase and trypsin inhibitors. Results from SDS-PAGE revealed 45 fractions with well-defined bands ranging from ~28 to ~401 kDa in larvae and adults, we found the main differences between the samples from different food matrices within the 75–100 kDa range. Hemolymph of adults from the coarse coconut fiber food matrix treatment showed a single band with a molecular weight close to 250 kDa, probably associated with a storage protein such as lipophorins. The food matrix with a coarse bulking agent had a high concentration of ammoniacal nitrogen, suggesting high microbial activity. In conclusion, the particle size of the bulking agent of the food matrix changes the bioavailability of protein in hemolymph in the adult regardless of the total concentration of protein. Also, when the particle size of the bulking agent favored the F/P ratio, higher larval density resulted in higher individual larval weight, larval yield, and adult emergence.
A critical issue point in diet management is maximizing density as a strategy for reducing costs. Artificial diets elaborated with large particle sizes have increased volume, possess high porosity and aeration capacity, are more penetrable and facilitate the movement of larvae and increase the bioavailability of nutrients. We report on an experiment aimed at determining if the bulking agent in the diet facilitates feeding and could increase the capacity to support high larval densities with a minimal effect of competition on life‐history traits of Anastrepha ludens. The results indicate that density affected larval and pupal weight, but not pupation at 24 h, adult emergence and flier percentage, which remained unchanged. However, there was an increase in yield and bioconversion. Larvae in high‐density conditions aggregated to increase the effect of regurgitation of amylases and proteases as a strategy to metabolize the food prior to ingestion through enzymes secreted in the saliva, contributing thus to feeding facilitation and the uptake of ingested food, which decreased the negative impact of competition under high‐density conditions. High density leads to an increase in food consumption and a concomitant increase in digestive enzyme activity, contributing to the bioavailability of macronutrients—proteins, carbohydrates and lipids—in the diet. Identifying the properties of bulking agents and other ingredients and their interaction under high‐density conditions is essential to develop novel artificial diets and improve the mass‐rearing strategies for the SIT.
In this study, the antifungal, biosurfactant and bioemulsifying activity of the lipopeptides produced by the marine bacterium Bacillus subtilis subsp. spizizenii MC6B-22 is presented. The kinetics showed that at 84 h, the highest yield of lipopeptides (556 mg/mL) with antifungal, biosurfactant, bioemulsifying and hemolytic activity was detected, finding a relationship with the sporulation of the bacteria. Based on the hemolytic activity, bio-guided purification methods were used to obtain the lipopeptide. By TLC, HPLC and MALDI-TOF, the mycosubtilin was identified as the main lipopeptide, and it was further confirmed by NRPS gene clusters prediction based on the strain’s genome sequence, in addition to other genes related to antimicrobial activity. The lipopeptide showed a broad-spectrum activity against ten phytopathogens of tropical crops at a minimum inhibitory concentration of 400 to 25 μg/mL and with a fungicidal mode of action. In addition, it exhibited that biosurfactant and bioemulsifying activities remain stable over a wide range of salinity and pH and it can emulsify different hydrophobic substrates. These results demonstrate the potential of the MC6B-22 strain as a biocontrol agent for agriculture and its application in bioremediation and other biotechnological fields.
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